In the fall sitcom “Mom,” Anna Faris’s newly sober Christy desperately wants to be different from her estranged mother. An emotionally brittle waitress, Christy blames all of her hardest problems — addiction, terminal cynicism, bad choices in men — on the woman who raised her.

But life, TV, sobriety, and comedy have another plan for Christy, as Rod Serling might have put it on “The Twilight Zone.” Who does she run into at an Alcoholics Anonymous meeting but her passive-aggressive mother, Bonnie, the cause of all her woe. A self-centered, spiky, and funny lady played with brilliant timing by Allison Janney, Bonnie fully intends to reconnect with her daughter and bond with Christy’s two kids. She latches on like a barnacle.

And so, like many adult children in the fall TV season, Christy can’t just deal with her parent issues in therapy, or at AA meetings, or on the telephone from across the country. She will be living in the parenthood, face to face and tooth and nail with her irritant.

The network lineups have reached one of those uncanny trope intersections where a group of shows are working the same theme at the same time: adults and their parents, multi-generational families, the Yiddish “meshpokha.” Along with “Mom,” from hitmaker Chuck Lorre of “The Big Bang Theory,” there’s “Dads,” “The Goldbergs,” “Back in the Game,” “Sean Saves the World,” “The Millers,” and “The Crazy Ones.” They join a number of preexisting series — most notably “Modern Family” and “Raising Hope” — to form a full-on trend.

Older parents on TV used to be special guest stars — Elliott Gould, Shirley Jones, Laurie Metcalf — who’d show up for an episode or two every season. The central characters on workplace and “Friends”-like ensemble comedies would receive visits from their folks — or sometimes, as in, “Sex and the City,” not even that. Now, they’re regulars, notably James Caan and George Segal as gruff grandpas on “Back in the Game” and “The Goldbergs,” respectively. Seth MacFarlane’s “Dads” is lame, but it features two live-in fathers. Peter Riegert torments Seth Green with his crankiness; Martin Mull embarrasses Giovanni Ribisi and his family by going naked around the house. Meanwhile the typically nutty Robin Williams gets in his daughter Sarah Michelle Gellar’s hair on “The Crazy Ones.”

And the adult children often have kids too. Shows such as “The Office,” “Parks and Recreation,” and “30 Rock,” have followed the path of “Scrubs,” “Will & Grace,” “Seinfeld,” and “Friends” in focusing on single people in their 20s and 30s. Once babies start showing up on sitcoms like those, as one has recently on “How I Met Your Mother,” the end is in sight. But these newer shows tend to begin with kids and teens on the scene. On “The Goldbergs,” the 1980s-set series is essentially seen through the eyes of youngest son Adam, who is based on show creator Adam F. Goldberg.

All three generations are in a house together on many of these sitcoms, slinging barbs across the kitchen table, the elders ensconced in the lives of their children and grandchildren on a daily basis. “Everybody Loves Raymond” was a pioneer, in some ways, of the current trend, except that the children on that show were rarely featured. On this new batch, the kids are as prominent as the grandparents, and often their bond is the source of both humor and poignancy. On “Back in the Game,” Caan’s tough guy goes from not being sure of his grandson’s name to coaching him in baseball and romance. Aww.

Monty Brinton/CBS

Anna Faris (left) and Allison Janney in the CBS comedy “Mom.”

Naturally, this trend is partly a cloning situation, since the most popular sitcom of recent years — and the winner of the last three best-comedy Emmys — is the quintessential multigenerational sitcom “Modern Family.” Once a show succeeds on TV, it automatically spawns other similar projects hoping to borrow some of its moment. In a way, it’s odd that shows blending together three generations — and three potential demos — have become the ticket right now in Hollywood; it rolls counter to the niche-ification of TV, which targets shows to ever-more specific audiences. But “Modern Family” hit it big, and it hit a nerve.

That nerve: More and more Americans are living in multigenerational homes. The number of households with multiple generations has risen by 13 percent since 2008, and it’s still rising. The troubled economy has forced the situation, to some extent, throwing the savings of elders — who are living longer — into jeopardy and pushing their children out of jobs. That’s a hard spot to be in for many adults, but it’s also ripe for humor; we have to come to terms with our families, as the ability to simply break off into a nuclear unit diminishes. And when everyone gets along and has plenty of room to breathe, comedy does not usually ensue.

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